Field of the Invention
The present invention relates to a fluorocopolymer composition having improved transparency, more particularly, it relates to a film or sheet made of a fluorocopolymer composition having improved transparency and high ultraviolet ray absorbancy and high heat aging resistance.
Description of the Prior Arts
Ethylene-tetrafluoroethylene type copolymers have been known as melt processable materials having excellent heat resistance, chemical resistance and electrical and mechanical characteristics.
The ethylene-tetrafluoroethylene type copolymers having excellent weather durability can be effectively used as protective coating materials for various products. For example, the protective effect can be attained by covering various products with the ethylene-tetrafluoroethylene type copolymer film or by coating various products by a heat melt coating method. It is also possible to attain the protective cover by using a composite film prepared by laminating a common synthetic resin film with the ethylene-tetrafluoroethylene type copolymer film.
The inventors have studied and found that the ethylene-tetrafluoroethylene type copolymer film is not suitable for the usages requiring transparency because the transparency of the film is remarkably lowered depending upon an increase of the thickness of the film.
Various methods for improving transparency of crystalline polymers have been proposed. For example, the method of modifying a polymer itself, the method of quenching in a molding process of a polymer and the method of adding a suitable additive have been proposed. The method of adding an additive is preferable from the viewpoint of the accomplishment of the purpose without modifying the synthesis of the polymer and the molding process. It has not been considered to improve transparency by an addition of an additive to a ethylene-tetrafluoroethylene type copolymer.